Five-grade motor oil for internal combustion engines

ABSTRACT

A five-grade motor oil composition for gasoline internal combustion engines having improved oil consumption and lowtemperature cranking characteristics comprises a base oil blend of two solvent extracted neutral mineral oils and a dewaxed and dearomatized catalytically cracked mineral oil stock, in combination with suitable lube oil additives. The finished oil formulation meets the requirements for a SAE 5W-40 motor oil.

United States Patent [191 Schieman [451 Mar. 25, 1975 1 FIVE-GRADE MOTOROIL FOR INTERNAL COMBUSTION ENGINES [76] Inventor: Richard D. Schieman,188

Moorewood Ave., Avon Lake, Ohio 44012 [22] Filed: Feb. 2, 1973 [21]Appl. No.: 329,033

Related US. Application Data [63] Continuation-impart of Ser. No.202,650, Nov. 26,

1971, abandoned.

3,595,967 7/1971 Riedel et a1, 252/327 E X OTHER PUBLICATIONS Smalheeret al., Lubricant Additives, 1967, pp. 28.

Primary Examiner-Patrick P. Garvin Assistant Examiner-Andrew H. MetzAttorney, Agent, or Firm-Herbert D. Knudsen; Sherman J. Kemmer; John F.Jones [57] ABSTRACT A five-grade motor oil composition for gasolineinternal combustion engines having improved oil consumption andlow-temperature cranking characteristics comprises a base oil blend oftwo solvent extracted neutral mineral oils and a dewaxed anddearomatized catalytically cracked mineral oil stock, in combinationwith suitable lube oil additives. The finished oil formulation meets therequirements for a SAE 5W-40 motor oil.

10 Claims, N0 Drawings FIVE-GRADE MOTOR OIL FOR INTERNAL COMBUSTIONENGINES This application is a continuation in part of US. Pat. Ser. No.202,650 filed Nov. 26, 1971 and now abandoned.

This invention relates to a motor oil composition for gasoline internalcombustion engines. More particularly this invention relates to ablended motor oil base stock that will provide adequate lubrication forinternal combustion engines despite extreme climatic conditions.

Normally, lubricating oils must provide minimal wear in an engine underoperating temperatures at the cylinder walls in the combustion zoneranging from well below F. on a winter morning to well above 400F. Toperform this function satisfactorily, the oil must have thermalstability, shear stability and a resistance to breaking down intoharmful deposits which show up as varnish within the engine. Anotherimportant criterion for motor oil performance is that it have lowconsumption in an engine, particularly because environmental pollutioncaused by automobile emissions is of concern.

A market has been developed for multi-grade motor oils which besideshaving all of the characteristics desired in a superior motor oil shouldprovide adequate lubrication throughout the year regardless of climaticconditions or severity of usage.

lt is therefor an object of this invention to provide a base oil for amotor oil formulation which comprises a unique blend of several refinerylubricating oil stocks in certain specific proportions which when usedin con junction with well known multi-functional dispersantdetergentadditives, viscosity index improvers, and pour point depressants will beconsumed at very low levels in the operation of the engine and will meetthe required specifications for a five-grade SAE 5W-40 crankcase oil.

A serious problem generally associated with 5W grade motor oils is oilconsumption. It has long been recognized that while 5W oils haveexcellent low temperature cranking properties, they usually are limitedto use at ambient temperatures not exceeding 60F. due to undesirable oilconsumption characteristics. At the same time oils of W grade areusually restrictive to low temperature cranking characteristics and arenot useful below 0F., however they do not have the oil consumptionproblems above 60F. associated with the SW oils. No known blend ofrefined petroleum-base has previously been described which will meet thespecifications required for a multi-grade 5W4O motor oil having bothsatisfactory consumption properties and low-temperature crankingproperties. It is therefor a further object of this invention to providea base oil blend for a SAE 5W-40 oil which satisfies both of the abovecriteria.

The most preferred oils of the instant invention provide a finished5W-40 motor oil wherein no more than 12 volume percent of the oil boilsbelow 725F., has a minimum 300F. viscosity of 6.5 centistokes, a minimum210F. viscosity of 14.7 centistokes, a maximum 0F. viscosity of 12poises (cold crank simulator viscosity) and a maximum consumption ratein the engine of about 5.8 quarts/64 hours of oil as defined by theSequence IIIC test (SAE-General Motors-6041).

In accordance with this invention, the base oil for the multi-grademotor oil comprises a specific blend of two selected solvent extractedneutral mineral oils, one having a viscosity of about 100 to about 150SSU preferably about 140 SSU at 100F., and the other having a viscosityof about 700 to about 800 SSU preferably about 750 SSU at 100F.,(hereinafter referred to as SEN 100-150 and SEN 700-800 respectively)and a second component which is dewaxed and dearomatized catalyticallycracked mineral oil stock having an average viscosity of about to aboutSSU preferably about 85 SSU at F. (herein referred to as HVl 75-90 oil).

Solvent extracted neutral oils are well-known standard mineral oilrefinery stocks. The HVl 75-90 oil is an end product obtained byfractionating the effluent from a catalytic cracking zone in a tower,running off the bottoms from the tower into a catalyst separation zonewhere the catalyst fines are settled out, decanting the supernatantphase called cycle oil or decanted oil, and extracting the decanted oilwith a solvent for the removal of aromatics. The extract phasecontaining the aromatics is removed, and the raffinate phase containingthe paraffinic stock is led to a dewaxing zone where wax is separated,leaving a dewaxed oil product which is the feed stock for the HVI oilused. The HVl 759O oil is obtained by fractionally distilling thisfeedstock. A process for obtaining a wax composition from a catalyticcracking stock, leaving a dewaxed oil product, is described in US. Pat.No. 2,660,553.

The base oil of this invention comprises a carefully balanced mixture ofthe aforementioned refinery stocks so that a light component and a heavycomponent are formulated and are combined to fulfill the SAE SW and theSAE 40 requirements of the multigrade motor oil. The light componentwhich fulfills the SAE5W requirement of the motor oil comprises a blendof two fractions of the dewaxed, dearomatized, fractionatedcatalytically cracked stock, which has superior thermal stability ascompared with solvent extracted neutral oilsof comparable boiling range,and a unique ability to reduce the viscosity of 0F. without decreasingthe viscosity at 210F. in the same ratio. The heavy component whichfulfills the SAE-40 requirement is derived from a blend of the SEN100-150 oil and the SEN 700-800 oil. The properties of typical mineraloil stocks blended to formulate the motor oil of this invention aregiven in Table l.

The high boiling range of the light component of this lubricating oilformulation is uniquely obtained by combining two fractions of thedewaxed, dearomatized, catalytically cracked stock in certain definiteratios which apparently azeotrope, thereby retaining the high boilingrange while reducing viscosity. It is highly important that a minimumamount of this light component boil below 725F. and that the 210F.viscosity remain as high as possible in order to minimize the quality ofthe oil consumed by the engine. The trend in oil consumption by theengine as related to the amount of oil in the finished oil boiling below725F. is illustrated by the data given in Table II. These data showwithin limits of experimental error that oils containing substantiallymore than 25 volume percent of components boiling below 725F. increaseconsumption above the tolerable limits. Preferred are light componentswhere no more than 15 volume percent boil below 725F.,

and most preferred are those light components where no more than 12volume percent boil below 725F.

In order for the light component of this base oil formulation to meetthe consumption restriction and to fulfill the SW requirement in thefinished oil, the light component must have a minimum viscosity at 210F.of about 3.2 centistokes, a maximum viscosity at F. of about 5.9 poises,coupled with a restrictive boiling range of between about 650 to 800F.with no more than about 25 percent by volume of the oil boiling below725F. The light component of the base oil of this invention isconveniently a blend of from about to 18 percent by volume of an oilfraction of a dewaxed, dearomatized, catalytically cracked stock havinga maximum of about 80 percent of the oil by volume boiling below 725F.,a 210F. viscosity in the range of from about 2.8 to 2.9 centistokes, a100F. viscosity of from about 11.5 to 11.9 centistokes and a 0 F.viscosity of from about 2.2 to 2.9 poises, combined with from about 82to 95 percent by volume of a dewaxed, dearomatized, catalyticallycracked oil fraction having a maximum of 15 percent by volume of the oilboiling below 725F., a 210F. viscosity of from about 3.8 to 4.0centistokes, a 100F. viscosity of from about 18.7 to 19.0 centistokesand a 0F. viscosity of from about 4.5 to 5.5 poises. Typicalcatalytically cracked oil fractions suitable for use in the lightcomponent of the base oil formulation are shown in Table l. The lightcomponent of the base oil could also be prepared from a single fraction.

The ratio of the two oil fractions that constitute the base oil may varyto some extent with the type of additive employed in the finished oil,since in instances where the additive contains a diluent oil, thevolatility of the base oil must be adjusted in accordance with thevolatility of the diluent oil employed.

The heavy component of the base oil in this invention in order tofulfill the SAE 40 requirement of the finished oil must have a 300F.viscosity of at least 2.5 centistokes in order to provide sufficienthydrodynamic film strength at high temperatures, a minimum 210F.viscosity of about 6.4 centistokes, a maximum 0F. viscosity of about20.0 poises and with little or no volume percent of the oil boilingbelow 725F.

The heavy component having the above properties is obtainable byblending from about 70 to about 85 preferably 72 to 84 volume percent ofa SEN 100-150 oil with from about 15 to about 30 preferably 16 to 28volume percent of a SEN 700-800 oil, the properties of typical oilsbeing given in Table 1.

Although the requirements for a 5W-40 base oil can be essentially metwith the oil blend comprising the light component of the presentformulation, there is need for the heavy component to fulfill the 300F.viscosity requirement essential for adequate film strength of the oil athigh temperatures. Concomitantly, the heavy component should haveproperties which do not increase the 0F. viscosity of the base oilformulation to above about 5.7 poises. Such an oil is obtained with theblend of a SEN 700-800 oil with a SEN 100-150 oil.

While a blend of the SEN 100 oil and the SEN 750 oil meet theviscometric requirements for the base oil at 0F., minor problemsassociated with volatility occur with this particular formulation.However, the SEN 140 oil in the heavy component blend can be replacedwith a SEN 100 oil provided the boiling range of the SEN 100 isrestricted to within approximately 720 to 835 F. It is again apparentthat the initial part of such an oil is closely restricted to the regionof 725F. Viscometrically such an oil must have a viscosity of from about3.9 to 4.2 centistokes at 210F. and a maximum viscosity of about 6.0poises at 0F.

To attain a base oil that meets the viscosity and volatility criteriafor the finished five-grade motor oil, the light and heavy componentsare blended in amounts ranging from about to parts of the lightcomponent with from about 15 to 30 parts of the heavy component on avolume basis. A typical base oil would have a maximum of about 10 volumepercent of the oil boiling below 725F. with the following viscometricproperties:

2.0 centistokes Minimum Viscosity at 300F.

4.0 centistokes Minimum Viscosity at 210F.

The additives to be added to the base oil formulation in order to obtaina finished crankcase oil with the proper SAE specification are thosethat are available commercially, such as the A.P.l. Service S.E.-typeadditives. 1n the instant formulation, two additives which are preferredto be combined with the base oil are a viscosity index improver and amulti-functional additive which is also adetergent-dispersant-inhibitor-type additive. A representative additiveof the former type is polymethylmethacrylate which typically may have aspecific gravity of about 0.9, a viscosity at 210F. of about 4200 SSU,and viscosity at F. of about 63,000 SSU with a pour point of +25F. Arepresentative additive of the latter type typically has a specificgravity of 0.95, a viscosity at 210F. of 156 SSU and contains minorquantities of magnesium, nitrogen, phosphorus, sulfur and zinc.Chemically this additive contains zinc dialkyl dithiophosphate andcalcium alkyl phenates as oxidation inhibitors, a succinimide as anashless dispersant and magnesium sulfonate as a detergent.

A typical oil formulation falling within the limits specifiedhereinabove is illustrated by the following example:

EXAMPLE In a tank maintained at F. and fitted with a continuous stirrerwere blended 1335 gallons of a viscosity index improver consisting ofpolymethylmethacrylate 19,110 gallons of a l-lVl 85 oil consisting of12.9 vol ume percent of a fraction of a dewaxed dearomatized,catalytically cracked stock having a 210F. viscosity of 2.85 centistokesand a 100F. viscosity of 11.5 centistokes, and 87.1 volume percent of afraction having a 210F. viscosity of 3.89 centistokes and a 100F.viscosity of 19.01 centistokes. In a separate tank at 140F. were mixed,with continuous stirring, 3450 gallons of SEN 140 oil, 1320 gallons ofSEN 750 oil, 1335 gallons of the above viscosity index improver and 3450gallons of a detergent-dispersant-inhibitor additive comprising amixture of a zinc dialkyl dithiophosphate, a calcium alkyl phenate,magnesium sulfonate and a succinimide. To this mixture were added theabove blend of l-lVl 85 oil and viscosity index improver. The final oilblend fulfilled the necessary requirements for a five-grade SAE 5W-40motor oil.

TABLE 1 Cat Cracked SEN Dewaxed Stocks SEN 100 SEN 140 750-800 Viscosity300F., Cs 1 5 2.0 2.3 5.1 Viscosity 210F.. Cs 2.85 3.89 5.0 14.23Viscosity I()()F., Cs 11.5 19.01 21.75 30.37 160.0 Viscosity F.. po1scs2.8 5.5 6.15 l 1.1 100.() Distillation 0F., 760 mm* lBP 622 690 700 719722 2 647 722 735 865 5 652 714 730 748 892 662 721 733 753 904 670 73 l740 762 922 50 693 750 753 785 964 90 732 790 789 835 1035 95 747 812808 860 1032 E.P. 770 816 818 880 'ASTM D-l 160 TABLE 11 Effect of 725F.Component on Oil Consumption of Finished Oil Oil Type 10W-40 10W 5W-405W-4O 5W-4O 5W-40 725F. Component, 0 17 34.5 20 12 9 Vol.71* OilConsumption, 2.28 4.0 4.43 3.42 2.0 2.94 Oz/Hr.

*ASTM D-1160 We claim: extracted neutral 011 of about 140 SSUviscosity 1. A blended base oil composition for. use in a fiveat 100F.,and grade SAE 5W-40 motor 011 comprising a blend ofthe- 2. from about 16to 28 parts by volume ofa solvent following mineral oil components:extracted neutral oil of about 750 SSU viscosity,

component (A) which consists essentially of a mixat 100F.,

ture of said component (A) having a minimum viscosity at 1. from about70 to 85 parts by volume ofa solvent 300F. of 2.5 centistokes, a minimumviscosity at extracted neutral oil of about 100-150 SSU vis- 210F. of6.0 centistokes, a maximum viscosity of 0F. cosity at 100F., and of 20.0poises, with zero percent of the oil boiling 2. from about 15 to 30parts by volume of a solvent below 725F; and I extracted neutral oil ofabout 700-800 SSU viscomponent (B) which consists essentially of a blendcosity, at 100F., of dewaxed oils obtained from an essentially arosaidcomponent (A) having a minimum viscosity at maticfree catalyticallycracked stock, said blend 300F. of 2.5 centistokes, a minimum viscosityat having a minimum viscosity of 210F. of 3.2 centi- 210F. of 6.0centistokes, a maximum viscosity at 0F. stokes, a maximum viscosity at01 of 5,9 poises of 20.0 poises, with little or none of the oil boilingand a maximum of 15 percent by volume of the debelow 725F.; and waxedoils boiling below 725F.;

component (B) which consists essentially of l-lVl and wherein component(B) comprises from about -90 dewaxed oil obtained from an essentially topercent by volume of the total base oil composiaromatic-freecatalytically cracked stock said de- 5 tion. waxed oil having a minimumviscosity at 210F. of 3. The blended base oil composition of claim 1 3.2centistokes, a maximum viscosity at 0F. of 5.9 wherein component (B)consists essentially of a blend poises and a maximum of 25 percent byvolume of of the dewaxed oil boiling below 725F., 1. from about 5 to 18parts by volume of a fraction and wherein component (B) comprises fromabout 70 60 of a dewaxed, catalytically cracked stock having to percentby volume of the total base oil composia viscosity at 210F. of fromabout 2.8 to 2.9 cention. tistokes, a maximum viscosity at 0F. of 2.9 2.A blended base oil composition of claim 1 for use poises, and a maximumof 80 percent by volume in a five-grade SAE 5W-40 motor oil comprising aof said oil fraction boiling below 725F.; and blend of the followingmineral oil components: 5 2. from about 82 to parts by volume of afraccomponent (A) which consists essentially of a mixture of 1. fromabout 72 to 84 parts by volume of a sol ent tion from said catalyticallycrackedstock having a viscosity at 210F. of from 3.8 to 4.0 centi- Lflemmaza um viscosity at -s 51 -9 and a maximum of 15 percent by volumeof said oil fraction boiling below 725F.

4. The blended base oil composition of claim 2 wherein the volume ratioof component (B) to component (A) is about 4 to 1.

5. In a five-grade SAE 5W-4O motor oil with excellent consumptionproperties and thermal and wear stability having a measured viscosity atF. not to exceed 12.0 poises, a minimum viscosity at 210F. of 14.7centistokes, a minimum viscosity at 300F. of about 6.5 centistokes, andwherein no more than 15 percent by volume of the oil boils below 725F.,comprising a multifunctional detergent-dispersant-inhibitor additive, aviscosity index improver and a base oil composition the improvementcomprising using as a base oil a blend of the following mineral oilcomponents:

component (A) which consists essentially of a mixture of l. from about70 to 85 parts by volume of a solvent extracted neutral oil of about100-150 SSU viscosity at 100F., and 2. from about 15 to 30 parts byvolume ofa solvent extracted neutral oil of about 700-800 SSU viscosityat 100F., said component (A) having a minimum viscosity at 300F. of 2.5centistokes, a minimum viscosity at 210F. of 6.0 centistokes, a maximumviscosity at 0F. of 20.0 poises with little or none of the oil boilingbelow 725F.; and

component (B) which consists essentially of l-lVl 75-90 dewaxed oilobtained from an essentially aromatic-free catalytically cracked stock,said dewaxed oil having a minimum viscosity at 210F. of 3.2 centistokes,a maximum viscosity at 0F. of 5.9 poises and a maximum of 25 percent byvolume of the dewaxed oil boiling below 725F.;

and wherein component (B) comprises from about 70 to 85 percent byvolume of the total base oil composition.

6. The five-grade motor oil of claim SWherein no more than 12 percent byvolume of the boil boils below 725F. and component (A) consistsessentially of 1. from 72 to 84 parts by volume of a solvent extractedneutral oil of about 140 SSU viscosity at 100F., and 2. from about 16 to28 parts by volume ofa solvent extracted neutral oil of about 750 SSUviscosity at 100F., with zero percent of the oil boiling below 725F.;and component (B) which consists essentially of a blend of dewaxed oilsobtained from an essentially aromaticfree catalytically cracked stock;said blend having a maximum of 15 percent by volume of the dewaxed oilsboiling below 725F.; wherein component (B) comprises to percent byvolume of the total base oil composition.

7. The five-grade SAE 5W40 motor oil composition of claim 4 whereincomponent (B) consists essentially of a blend of 1. from about 5 to 18parts by volume of a fraction of a dewaxed, catalytically cracked stockhaving a viscosity at 2 10F. of from about 2.8 to 2.9 centistokes, amaximum viscosity at 0F. of 2.9 poises, and a maximum of 80 percent byvolume of said oil fraction boiling below 725F.; and

2. from about 82 to parts by volume of a fraction from saidcatalytically cracked stock having a viscosity at 210F. of from 3.8 to4.0 centistokes, a maximum viscosity at 0F. of 5.5 poises and a maximumof 15 percent by volume of said oil fraction boiling below 725F.

8. The composition in claim 5 wherein said viscosity index improver ispolymethylmethacrylate and said multifunctional detergent additivecomprises a mixture of zinc dialkyl dithiophosphate, a calcium alkylphenate, a succinimide and magnesium sulfonate.

9. An HVl 75-90 dewaxed oil having an average viscosity of 75 to about90 SSU at F. obtained from an essentially aromatic-free catalyticallycracked stock, said dewaxed oil having a minimum viscosity at 210F. of3.2 centistokes, a maximum viscosity at 0F. of 5.9 poises and a maximumof 25 percent by volume of the dewaxed oil boiling below 725F.

10. The HVl 75-90 dewaxed oil of claim 9 wherein a maximum of 15 percentby volume of the dewaxed oil boils below 725F.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Q PATENT NO. 3 73455 DATED March 25 1975 1 Richard D. Schieman It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below: 0

Column 5 Table I SEN 100 SEN 140 and SEN 750-800 should read as followsSEN 100 SEN 140 SEN 750-800 Signed and Scaled this 7 Fifth Day ofOctober 1976 [SEAL] Arrest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer (umnrissioner ofParents and Trademarks

1. A BLENDED BASE OIL COMPOSITION FOR USE IN A FIVE-GRADE SAE 5W-40MOTOR OIL COMPRISING A BLEND OF THE FOLLOWING MINERAL OIL COMPONENTS:COMPONENT (A) WHICH CONSISTS ESSENTIALLY OF A MIXTURE OF
 1. FROM ABOUT70 TO 85 PARTS BY VOLUME OF A SOLVENT EXTRACTED NEUTRAL OIL OF ABOUT100-150 SSU VISCOSITY AT 100*F., AND
 2. FROM ABOUT 15 TO 30 PARTS BYVOLUME OF A SOLVENT EXTRACTED NEUTRAL OIL OF ABOUT 700-800 SSUVISCOSITY, AT 100*F., SAID COMPONENT (A) HAVING A MINIMUM VISCOSITY AT300*F. OF 2.5 CENTISTOKES, A MINIMUM VISCOSITY AT 210*F. OF 6.0CENTISTOKES, A MINIMUM VISCOSITY AT 0*F. OF 20.0 POISES, WITH LITTLE ORNONE OF THE OIL BOILING BELOW 725*F.; AND COMPONENT (B) WHICH CONSISTSESSENTIALLY OF HVI 75-90 DEWAXED OIL OBTAINED FROM AN ESSENTIALLYAROMATIC-FREE CATALYTICALLY CRACKED STOCK SAID DEWAXED OIL HAVING AMINIMUM VISCOSITY AT 210*F. OF 3.2 CENTISTOKES, A MAXIMUM VISCOSITY AT0*F. OF 5.9 POISES AND A MAXIMUM OF 25 PERCENT BY VOLUME OF THE DEWAXEDOIL BOILING BELOW 725*F., AND WHEREIN COMPONENT (B) COMPRISES FROM ABOUT70 TO 85 PERCENT BY VOLUME OF THE TOTAL BASE OIL COMPOSITION.
 2. fromabout 82 to 95 parts by volume of a fraction from said catalyticallycracked stock having a viscosity at 210*F. of from 3.8 to 4.0centistokes, a maximum viscosity at 0*F. of 5.5 poises and a maximum of15 percent by volume of said oil fraction boiling below 725*F.
 2. fromabout 16 to 28 parts by volume of a solvent extracted neutral oil ofabout 750 SSU viscosity at 100*F., with zero percent of the oil boilingbelow 725*F.; and component (B) which consists essentially of a blend ofdewaxed oils obtained from an essentially aromatic-free catalyticallycracked stock; said blend having a maximum of 15 percent by volume ofthe dewaxed oils boiling below 725*F.; wherein component (B) comprises70 to 80 percent by volume of the total base oil composition.
 2. fromabout 15 to 30 parts by volume of a solvent extracted neutral oil ofabout 700-800 SSU viscosity at 100*F., said component (A) having aminimum viscosity at 300*F. of 2.5 centistokes, a minimum viscosity at210*F. of 6.0 centistokes, a maximum viscosity at 0*F. of 20.0 poiseswith little or none of the oil boiling below 725*F.; and component (B)which consists essentially of HVI 75-90 dewaxed oil obtained from anessentially aromatic-free catalytically cracked stock, said dewaxed oilhaving a minimum viscosity at 210*F. of 3.2 centistokes, a maximumviscosity at 0*F. of 5.9 poises and a maximum of 25 percent by volume ofthe dewaxed oil boiling below 725*F.; and wherein component (B)comprises from about 70 to 85 percent by volume of the total base oilcomposition.
 2. from about 82 to 95 parts by volume of a fraction fromsaid catalytically cracked stock having a viscosity at 210*F. of from3.8 to 4.0 centistokes, a maximum viscosity at 0*F. of 5.5 poises and amaximum of 15 percent by volume of said oil fraction boiling below725*F.
 2. from about 16 to 28 parts by volume of a solvent extractedneutral oil of about 750 SSU viscosity, at 100*F., said component (A)having a minimum viscosity at 300*F. of 2.5 centistokes, a minimumviscosity at 210*F. of 6.0 centistokes, a maximum viscosity of 0*F. of20.0 poises, with zero percent of the oil boiling below 725*F; andcomponent (B) which consists essentially of a blend of dewaxed oilsobtained from an essentially aromatic-free catalytically cracked stock,said blend having a minimum viscosity of 210*F. of 3.2 centistokes, amaximum viscosity at 0*F. of 5,9 poises and a maximum of 15 percent byvolume of the dewaxed oils boiling below 725*F.; and wherein component(B) comprises from about 70 tO 80 percent by volume of the total baseoil composition.
 2. A blended base oil composition of claim 1 for use ina five-grade SAE 5W-40 motor oil comprising a blend of the followingmineral oil components: component (A) which consists essentially of amixture of
 2. from about 15 to 30 parts by volume of a solvent extractedneutral oil of about 700-800 SSU viscosity, at 100*F., said component(A) having a minimum viscosity at 300*F. of 2.5 centistokes, a minimumviscosity at 210*F. of 6.0 centistokes, a maximum viscosity at 0*F. of20.0 poises, with little or none of the oil boiling below 725*F.; andcomponent (B) which consists essentially of HVI 75-90 dewaxed oilobtained from an essentially aromatic-free catalytically cracked stocksaid dewaxed oil having a minimum viscosity at 210*F. of 3.2centistokes, a maximum viscosity at 0*F. of 5.9 poises and a maximum of25 percent by volume of the dewaxed oil boiling below 725*F., andwherein component (B) comprises from about 70 to 85 percent by volume ofthe total base oil composition.
 3. The blended base oil composition ofclaim 1 wherein component (B) consists essentially of a blend of
 4. Theblended base oil composition of claim 2 wherein the volume ratio ofcomponent (B) to component (A) is about 4 to
 1. 5. In a five-grade SAE5W-40 motor oil with excellent consumption properties and thermal andwear stability having a measured viscosity at 0*F. not to exceed 12.0poises, a minimum viscosity at 210*F. of 14.7 centistokes, a minimumviscosity at 300*F. of about 6.5 centistokes, and wherein no more than15 percent by volume of the oil boils below 725*F., comprising amultifunctional detergent-dispersant-inhibitor additive, a viscosityindex improver and a base oil composition the improvement comprisingusing as a base oil a blend of the following mineral oil components:component (A) which consists essentially of a mixture of
 6. Thefive-grade motor oil of claim 5 wherein no more than 12 percent byvolume of the boil boils below 725*F. and component (A) consistsessentially of
 7. The five-grade SAE 5W-40 motor oil composition ofclaim 4 wherein component (B) consists essentially of a blend of
 8. Thecomposition in claim 5 wherein said viscosity index improver ispolymethylmethacrylate and said multifunctional detergent additivecomprises a mixture of zinc dialkyl dithiophosphate, a calcium alkylphenate, a succinimide and magnesium sulfonate.
 9. An HVI 75-90 dewaxedoil having an average viscosity of 75 to about 90 SSU at 100*F. obtainedfrom an essentially aromatic-free catalytically cracked stock, saiddewaxed oil having a minimum viscosity at 210*F. of 3.2 centistokes, amaximum viscosity at 0*F. of 5.9 poises and a maximum of 25 percent byvolume of the dewaxed oil boiling below 725*F.
 10. The HVI 75-90 dewaxedoil of claim 9 wherein a maximum of 15 percent by volume of the dewaxedoil boils below 725*F.